Capacitor discharge ignition system

ABSTRACT

A capacitor discharge ignition system in which shut-off of the electronic switch is ensured by the use of an impedance means in series between the electronic switch and the primary winding of the ignition transformer, and by the use of a voltage responsive device to remove the triggering potential from the electronic switch immediately after the conduction of the electronic switch. Engine shut-off is ensured by the application of triggering potential to the electronic switch concurrently with the application of charging current to the ignition capacitor whereby the electronic switch remains conductive to prevent the accumulation of a charge on the ignition capacitor. A novel twolegged core and physical arrangement of the coils and other components of the system is also disclosed for one and multiple cylinder operation.

United States Patent 1191 Burkett et a1.

[ CAPACITOR DISCHARGE IGNITION SYSTEM [75] lnventors: Wiliord Benson Burkett, Pacific Palisades; Donald Eugene Martin, Costa Mesa; Richard Harry Sparks, Westminster, all of Calif [73] Assignee: McCulloch Corporation, Los

Angeles, Calif.

[22] Filed: June 15, 1973 [21] App1.N0.:370,371

[52] US. Cl. 123/148 E; 315/209 [51] Int. Cl. F02p 3/06 {58] Field of Search 123/148. 149; 307/252 L, 307/252 M, 252 N; 315/209 CD, 209 SC [56] References Cited UNITED STATES PATENTS 3,318.358 5/1967 Potts 307/252 W 3,398,353 8/1968 Noddin et a1. 123/148 E 3,461,851 8/1969 Stephens i i i 123/148 E 3,554,179 1/1971 Burson H 123/148 E 3,623,467 11/1971 Piteo 123/148 E 3.648.675 7/1970 Gemandcr 123/148 E 1 July 15, 1975 Jacobs 123/148 E Swift 123/148 E [57] ABSTRACT A capacitor discharge ignition system in which shutoff of the electronic switch is ensured by the use of an impedance means in series between the electronic switch and the primary winding of the ignition transformer, and by the use of a voltage responsive device to remove the triggering potential from the electronic switch immediately after the conduction of the electronic switch Engine shut-off is ensured by the appli cation of triggering potential to the electronic switch concurrently with the application of charging current to the ignition capacitor whereby the electronic switch remains conductive to prevent the accumulation of a charge on the ignition capacitor. A novel two-legged core and physical arrangement of the coils and other components of the system is also disclosed for one and multiple cylinder operation.

21 Claims, 7 Drawing Figures SHEET FLYWHEEL ROTATION PAITFEF'IEHJUL 15 1925 3,894.52;

SHEET 2 CAPACITOR DISCHARGE IGNITION SYSTEM BACKGROUND OF THE INVENTION The present invention relates to capacitor discharge ignition systems and more specifically to an ignition system and method having novel electronic switch shutoff and engine shutoff features.

Capacitor discharge ignition systems are well known. Such systems generally utilize the rotation of a magneto in flux cutting proximity to induce a current in the charging coil of the capacitor and the subsequent inducing of a trigger current by continued magneto rotation in a trigger coil connected to the gate or trigger electrode of the electronic switch. The electronic switch traditionally employed has been a silicon controlled rectifier (SCR) which conducts in a single direction respectively to a predetermined anode cathode bias and the application ofa triggering pulse to the gate thereof. It is a characteristic of SCRs that conduction. once commenced, continues so long as the necessary anode-cathode bias is present irrespective of the continued presence of the triggering pulse. Shutoff of the SCR is thus achieved by the loss of the necessary anode-cathode potential as the capacitor discharges rather than by the loss of triggering potential on the gate of the SCR.

A continuing problem in the utilization of electronic switches such as SCRs in capacitor discharge ignition circuits lies in the substantially continuous conduction thereof due to the continued presence of a triggering potential on the gate electrode as the charging current reestablishes the necessary anode-cathode bias. The substantial continuous conduction of the SCR thus distributes the energy of the charging current over a time interval sufficient to reduce the amplitude below that which is required for ignition. Cutoff of the SCR between the discharge of the capacitor and the generation of a subsequent charging current is thus necessary.

It is accordingly an object of the present invention to obviate this and other deficiencies of the known prior art capacitor discharge ignition systems and to provide a novel method and system for the ignition control of an internal combustion engine.

Another object of the present invention is to provide a novel method and system for insuring the nonconduction of an SCR in a capacitor discharge ignition system between the charging cycles of the capacitor.

Still another object of the present invention is to provide a novel method and system for the timely removal of triggering potential from the gate of an SCR in a capacitor discharge ignition system.

Yet still another object of the present invention is to provide a novel method and system for delaying the achievement of an anode-cathode bias sufficient for the conduction of an SCR in a capacitor discharge ignition system.

A further object of the present invention is to provide a novel method and system for insuring engine cutoff by insuring the continued conduction of the electronic switch in the capacitor discharge ignition system.

A still further object of the present invention is to provide a novel physical arrangement of a twolegged core and ignition circuit components whereby a significant reduction in size and weight may be achieved.

Yet a further object of the present invention is to provide a novel method and system for component sharing in a plural cylinder capacitor discharge ignition system.

Yet still a further object of the present invention is to provide a novel physical arrangement of components for a plural cylinder capacitor discharge ignition system.

These and many other objects of the present invention will become apparent to one skilled in the art to which the invention pertains from a perusal of the following detailed description when read in conjunction with the appended drawings.

THE DRAWINGS FIG. I is a schematic circuit diagram of the circuit of the present invention;

FIGS. 2A and 2B are waveforms of the current induced in the trigger coil at different engine speeds;

FIG. 3 is a pictorial elevation in partial section illustrating the physical configuration of the system;

FIG. 4 is a schematic circuit diagram of the circuit of the present invention for a two-cylinder engine;

FIG. 5 is a schematic top plan view illustrating the physical arrangement of the coil systems and flywheel magnets; and.

FIG. 6 is a section in elevation taken through lines 66 of FIG. 5.

THE DETAILED DESCRIPTION With reference now to FIG. I wherein the circuit of the present invention is schematically illustrated. a suitable conventional magneto or magnet carrying flywheel may be rotated in a counterclockwise direction as illustrated by the arrow I0. A coil 12 may be disposed in flux cutting proximity to the magneto and may be connected to a capacitor 14 by means of diodes I6 and I8. The capacitor 14 may also be connected in series circuit with a suitable conventional electronic switch such as an SCR 20. a diode 22 and the primary winding 24 of a high voltage transformer 26. The secondary winding 28 of the high voltage transformer 26 may be connected through a suitable conventional distributor (not shown) to one or more gap ignition devices such as the illustrated spark plug 30. The SCR 20 and the diode 22 may be connected in parallel with a diode 32.

The coil 12 of the circuit as above described provides a charging current to the capacitor 14 through the diodes I6 and 18. It is to be understood that the number of diodes in the charging circuit may vary so long as they are collectively sufficient in voltage rating to withstand the high reverse bias occasioned by the charge coil 12 as will be subsequently explained. The diode 32 must have a voltage rating sufficient to withstand the preignition charge of the capacitor 14 and performs a commutating function as the circuit rings" with the discharge of the capacitor 14 through the primary winding 24 of the transformer 26.

The trigger electrode or gate 34 of the SCR 20 may be connected to one end of a coil 36 also disposed in flux cutting proximity to the path 10 of the magneto. The coil 36 may be disposed in substantially the same spatial relationship with the magneto as is the coil 12 and the other end of the coil 36 may be selectively grounded through the operation of a suitable conventional electronic or manually operable switch 38.

The gate 34 of the SCR 20 may be connected in series with a pair of resistors 40 and 42 to one end of a coil 44 disposed in flux cutting proximity to the path 10 of the magneto. As will be explained later in greater detail. the coil 44 precedes the coils l2 and 36 in the direction of rotation of the magneto. The coil 44 may be connected in parallel with a resistor 46 and the resistor 40-resistor 42 junction grounded through a voltage responsive device such as the illustrated breakdown diode 48.

In operation with the switch 38 in the illustrated open position and the SCR nonconducting. the rotation of the flywheel magnet in flux cutting proximity to the coils l2 and 36 induces a current in the coil 12 but not in the coil 36 due to the open circuit provided by the switch 38. The current induced in the coil 12 is passed through the diodes l6 and 18 to charge the capacitor 14. The polarity of the diode 32 and the nonconducting condition of the SCR 20 insure the lack of a discharge path for the capacitor 14 during the charging thereof with the current induced in the charging coil 12.

Continued rotation of the magneto will result in the rotation of the magnet carried thereby past the trigger coil 44 in flux cutting proximity thereto. The current thus induced in the trigger coil 44 passes through the resistor 46 to produce a voltage drop thereacross. This voltage drop also appears across the resistor 42 and the breakdown diode 48 which together act as a voltage divider to provide a positive potential at the resistor 40- resistor 42 junction and thus the gate 34 of the SCR 20.

When the potential on the gate 34 of the SCR 20 increases sufficiently with respect to the cathode thereof, the SCR 20 conducts due to the positive anode-tocathode bias provided by the charge on the capacitor 14 and the capacitor 14 is discharged through the SCR 20, the diode 22 and the primary winding 24 of the high voltage transformer 26. The current induced in the secondary winding 28 of the high voltage transformer 26 by the passage of current through the primary winding 24 thereof is applied to the appropriate gap ignition device 30. Thus the engine responsive rotation of the magneto alternately induces a charging current in the coil 12 to effect the charging of the capacitor 14 and the inducing of a trigger current in the trigger coil 44 to discharge the capacitor 14 through the high voltage transformer 26 by the firing of the SCR 20.

The resistor 42 limits the current which passes through the breakdown diode 48 upon the breakdown thereof. The resistor 40 performs a similar current limiting function to protect the gate 34 of the SCR 20.

The resistor 46 helps to prevent an untimely firing of the SCR 20 in that it effects a reduction in the amplitude of the positive current pulse illustrated as waveform 50 in FIG. 2A to that illustrated in phantom as waveform 52. There is a similar amplitude reduction from that illustrated as waveform 54 in FIG. 28 to that illustrated in phantom as waveform 56.

The difference between the waveforms of FIGS. 2A and 2B is primarily one of the speed of rotation of the magneto. As illustrated in FIG. 2B, the second positive excursion 58 of the current pulse might exceed the trigger level 60 of the SCR 20 and thus produce a misfire. The reduction in amplitude provided by the resistor 46 reduces this possibility at all engine speeds. The first positive excursion 62, while attenuated, remains sufficient for triggering the SCR 20 at all engine speeds.

An important feature of the present invention is the use of the diode 22 to insure cutoff of the SCR 20 between the inducement of triggering pulses in the trigger coil 44 and charge pulses in the charge coil l2. The SCR 20 must become nonconducting to eliminate the discharge path for the capacitor 14 since a significant charge must be accumulated on the capacitor 14 to achieve the desired ignition potential.

More specifically, the voltage drop across the diode 22 increases the cathode potential of the SCR 20 and thus increases the potential to which the gate of the SCR 20 must be raised to achieve the gate-cathode bias necessary for SCR conduction.

As earlier explained, the voltage drop across the breakdown diode 48 is substantially that of the gate 34 of the SCR 20 as the triggering potential is being developed across the resistor 46. The breakdown point of the diode 48 is desirably selected to be slightly in excess of the potential at which the SCR is rendered conductive. In this manner, the SCR 20 will be triggered by the rising gate 34 potential and shortly thereafter the excessive gate potential will be removed by the breakdown of the diode 48. In this manner, the trigger potential is reduced from the gate 34 of the SCR 20 almost immediately after the conduction of the SCR 20 and the likelihood of SCR cutoff materially increased with the reduction in gate-cathode bias as a result of the discharge of the capacitor 14. The breakdown diode 48 thus effectively decreases the possibility of gate saturation which would hold the SCR in conduction longer than desired.

Thus. the use of an impedance device such as the diode 22 or a small resistor to raise the cathode potential of the SCR 20 creates a delay in the reestablishment of sufficient gatecathode bias and thus increases the likelihood that the trigger potential will have been removed from the gate 34. The diodes 48 and 22 thus operate together to insure SCR cutoff and thus the continued firing of the ignition device 30.

One way of insuring engine shutdown is the cessation of the application of a gap ionizing potential to the ignition device 30. This may be accomplished in the present invention by the closure of the switch 38 so that current will be induced in the shutoff coil 36 in substantial coincidence with the generation of the charging current in the charging coil 12. The coincidence of generation and the same polarity of the two currents may be insured by the configuration and spatial location of the coils l2 and 36 with respect to the path 10 of the magneto.

With the switch 38 closed, the current induced in the shutoff coil 36 is applied across the resistor 40 and the breakdown diode 48 to provide a triggering potential at the gate 34 of the SCR 20 and thereby insure the conduction thereof as soon as the necessary anode-cathode bias has been established by the application of the charging current to the capacitor 14. A continuous discharge path for the capacitor 14 is thus provided and the buildup of a charge thereon thus prevented. The continuous discharge of the capacitor 14 effectively spreads the charging current over a time interval sufficiently long in duration that gap ionizing potential is not available for the ignition device 30. Engine shutdown is thus insured.

With reference to the physical structure illustrated in FIG. 3, a two-legged magnetic core is shown having the trigger coil 44 wound about one leg 66 thereof and the shut-off coil 36 wound about the other leg 68 thereof. The charging coil 12 as illustrated may be wound about the leg 68 of the core 64 in an overlying relationship with the shut-off coil 36. While it is desirable to wind the charging and shut-off coils 12 and 36 in this fashion, it is to be understood that the two coils may be axially displaced on the leg 68 of the core 64, or the shutoff coil wound in overlying relationship with the charge coil.

Disposed between the legs 66 and 68 of the magnetic core 64 may be the ignition capacitor 14 and a printed circuit board 70 by which may be carried the other electrical components of the circuit such as the SCR 20, trigger diode 48, etc. The capacitor 14 is illustrated as being connected to the primary winding 24 of the transformer 26. The secondary winding 28 is desirably wound about a cylindrical ferrite core 72 and the primary winding 24 of the transformer 26 is wound in an overlying relationship to the secondary winding 28. The output signal from the secondary winding 28 may be applied to the ignition device 30 of the circuit of FIG. 1 by way of an output terminal 74.

The arrangement illustrated in FIG. 3 has been utilized to reduce both the volume and weight of the ignition circuit to about one-fourth to one-third of the volume and weight normally associated with such ignition circuits. By the use of a ferrite core in the transformers, the transformer may be physically displaced from the remainder of the circuit thus enhancing the flexibility in mounting the system. The transformer may be potted with the remainder of the ignition circuit if desired. or potted and mounted as a separate unit.

The circuit of the present invention may also be adapted for multiple cylinder engines, for example and as illustrated in FIG. 4 in the context of a two-cylinder circuit, additional advantages may be achieved through the utilization of a common charging coil C and ignition capacitor 80 in parallel with a common diode 82. Also in parallel with the ignition capacitor 80 and the charging coil C are the two trigger circuits necessary for two-cylinder operation.

For example and with reference to the left-hand side of FIG. 4, the capacitor 80 may be connected through an SCR 84 and a diode 86 to the primary winding P, of a first cylinder high voltage transformer 88. The secondary winding S of the high voltage transformer 88 may be connected between the grounded interconnection of the diode 86 with the primary winding P and the ungrounded side of a first cylinder gap ignition device 90. A diode 92 may be connected in parallel with and in opposition to the conduction polarity of the SCR 84 and diode 86.

The trigger circuit for the SCR 84 may be identical to the trigger circuit earlier described in connection with FIG. I with the trigger electrode of the SCR 84 grounded through the series connection of a first cylinder shut-off coil S0 and a switch SW The trigger electrode of the SCR 84 may also be connected through a resistor 96 and a breakdown diode 98 to ground potential. The interconnection of the resistor 96 and the breakdown diode 98 may be connected through a resistor 100 in series with the parallel combination of a resistor 102 and the first cylinder trigger COll T].

Similarly and with reference to the right-hand side of FIG. 4, the ignition capacitor 80 may be connected to the charging coil C through a diode 82 and also to a second SCR 104, a diode I08 and the primary winding P of a second cylinder high voltage transformer 110. The grounded interconnection of the diode I08 and the primary winding P may be connected through the secondary winding S of the transformer I to the un- 6 grounded side of a second cylinder gap ignition device I 12.

The trigger electrode of the second cylinder SCR 104 may be grounded through the series connection of a second cylinder shut-off coil and a switch SW The trigger electrode of the SC R I04 may also be connected through a resistor I16 and a breakdown diode II8 to ground potential and the interconnection of the resistor I16 and the breakdown diode I18 grounded through a resistor I22 and the trigger coil T, associated with the second cylinder.

The operation of the shut-off coils SO, and 50 may insure the conduction of the SCRs 84 and I04 during the attempted charging of the capacitor 80 by the charging coil C in the manner earlier described in connection with FIG. 1. Thus, the simultaneous operation of the switches SW and SW: may be used to insure engine shut-off by preventing the charging of the ignition capacitor 80 to the ignition potential of the gap ignition devices and H2 as earlier described in connection with the circuit of FIG. 1.

Similarly, as described in connection with the circuit of FIG. I, the trigger diodes 98 and H8 insure the reduction of triggering potential to the trigger electrodes of the SCRs 84 and I04 to minimize the possibility of gate saturation causing the conduction thereof in the absence of a new trigger pulse so that the capacitor 80 may be charged anew from the current induced in the charging coil C.

The use of a single charging coil C and capacitor 80 for two cylinders requires the utilization of two flywheel magnets I21 and 124 illustrated schematically in FIG. 5. Also illustrated schematically in FIG. 5 is a third flywheel magnet I26 mounted on the radially inward edge of the flange portion I28 of the flywheel 130. As illustrated in FIG. 5 and in the cross sectional view of the flywheel illustrated in FIG. 6, a two leg core assembly I32 of the type illustrated in FIG. 3 may be mounted in flux cutting proximity to the radially outer edge of the flywheel so that rotation of the flywheel I30 induces a voltage in the charging coil C wound thereon twice during one complete rotation of the flywheel at I80 intervals.

A departure from the trigger coil assembly illustrated in FIG. 3 is required for the operation of a two cylinder engine circuit as described in connection with FIG. 4 in that two triggering coils T and T are required to generate the triggering signals at the proper sequence. With continued reference to FIGS. 5 and 6, a pair of coil assemblies 134 and 136 may be mounted internally of the flange 138 of the flywheel 130. These coil assemblies may be diametrically opposed and spaced equidistant from a charging coil assembly 132. By virtue of the arrangement illustrated, the capacitor 80 of FIG. 4 may be charged by the rotation of the flywheel magnet I24 past the coil assembly 132 and the SCR associated with one cylinder thereafter fired by the passage of the magnet 126 in flux cutting proximity to the trigger coil 136. Continued rotation of the flywheel in a clockwise direction will bring the flywheel magnet 12] in flux cutting proximity to the coil assembly 132 to again charge the capacitor 80 and will bring the magnet 126 in flux cutting proximity to the trigger coil assembly I34 to tire the SCR associated with the second cylinder.

The location of the flywheel magnets 121 and 124 on the outer radius of the flywheel and the location of the magnet 126 on the inner radius of the flange I28 achieves the desired isolation between the respective components. The polarity of the magnets and the orientation of the core assemblies may also be different to further the electromagnetic isolation such that the trigger magnet 126 will have no effect on the coil assembly 132 and the charging magnets 121 and 124 will have no effect on the trigger coil assemblies 134 and 136.

The operation of the circuit may be as earlier described with the resistors 100 and 120 limiting the current passing through the diodes 98 and 118 respectively upon the breakdown thereof.

ADVANTAGES AND SCOPE OF THE INVENTION As is readily apparent from the foregoing. the ignition system of the present invention achieves a substantial reduction in both volume and weight while simultaneously significantly improving the reliability over known systems. By means of an impedance such as a small resistor or diode connected in series between the cathode of the SCR and the primary winding of the ignition transformer. the cathode potential of the SCR may be raised such that the achievement of the SCR gate to cathode conduction bias is insufficient to maintain SCR conduction. This ensures turn off of the SCR between the desired ignition pulses. In addition. the use of a time or voltage responsive means to shunt the triggering potential away from the gate of the SCR immediately following the turn on of the SCR prevents the inadvertent conduction of the SCR upon the initial build up of the gate-cathode potential as a result of the charging of the ignition capacitor.

The use of an impedance means to reduce the amplitude of the minor peaks of the current induced in the trigger coil to a value below the triggering potential of the SCR renders the operation of the circuit of the present invention nonresponsive to the speed of magneto rotation.

The physical configuration of the components and the independent mounting of the ignition transformer on a ferrite core affords a compactness heretofore unknown. The transformer may be potted with the ignition circuit if desired. Moreover, the shut-off circuit of the present invention is a low voltage. low current circuit which is fire proof and which can be physically touched on the lead to the shut-off switch at any engine speed.

The circuit of the present invention may be utilized in connection with multiple cylinder engines either by means of a conventional distributor system or by means of a common charging coil and ignition capacitor with a separate trigger circuit for each cylinder. Timing for the operation of a multiple cylinder circuit may be achieved by the appropriate placement of flywheel magnets with isolation such as provided by the location of the charging and trigger current inducing magnets on opposite sides of the flywheel.

The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive. the scope of the invention being indicated by the appended claims rather than by the foregoing description. and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed:

1. An ignition circuit for an internal combustion engine comprising:

a capacitor;

means for periodically applying a unidirectional current to said capacitor responsively to engine rotation;

a discharge circuit for said capacitor. said discharge circuit including the primary winding of an ignition transformer and an SCR connected in series;

a trigger circuit means for periodically applying a triggering potential to the gate of said SC R responsively to engine rotation; and,

selectively operable means for periodically applying a triggering potential to the gate of said SCR during the application of said unidirectional current to said capacitor.

2. The circuit of claim 1 wherein said trigger circuit means includes voltage responsive means for interrupting the application of triggering potential to the gate of said SCR.

3. The circuit of claim 1 including at least one additional discharge circuit with the primary winding of an ignition transformer and an SCR connected in series; and,

a triggering circuit for each of said additional trigger circuits for periodically applying a triggering potential to the gate of the associated SCR responsively to engine rotation.

4. An ignition circuit for an internal combustion engine comprising:

a capacitor;

means for periodically applying a unidirectional current to said capacitor responsively to engine rotation in the forward direction;

a discharge circuit for said capacitor, said discharge circuit including the primary winding of an ignition transformer in series with electronic switch means;

a trigger circuit for periodically applying a triggering potential to said switch means responsively to engine rotation in the forward direction; and,

means for interrupting the application of triggering potential to said switch means responsive to said trigger circuit means.

5. The circuit of claim 4 wherein said triggering potential interrupting means is responsive to the potential of the gate of said switch means.

6. The circuit of claim 4 wherein said electronic switch is an SCR; and,

wherein said triggering potential interrupting means includes coil means and switching means for effectively shunting the current induced in said coil means away from the gate of said SCR.

7. The circuit of claim 6 including selectively operable means for periodically applying a triggering potential to the gate of said SCR in substantial synchronism with the application of said unidirectional current to said capacitor.

8. The circuit of claim 6 including impedance means connected in series with said coil means for limiting the triggering potential to a value nondestructive of said SCR at maximum engine speeds.

9. The circuit of claim 4 including selectively operable means for periodically applying a triggering potential to said switch means in substantial synchronism with the application of said unidirectional current to said capacitor.

10. The circuit of claim 4 including at least one additional discharge circuit for said capacitor, each of said additional discharge circuits including the primary winding of an ignition transformer in series with electronic switch means;

a trigger circuit for each of said additional discharge circuits for periodically applying a triggering potential to the associated switch means responsive to engine rotation; and,

means associated with each of said additional discharge circuit for interrupting the application of triggering potential to said switch means.

ll. An ignition circuit for an internal combustion en gine comprising:

a magnetic core having two legs adapted to be mounted adjacent to a rotating magnetic member of an engine with said legs displaced in the direction of rotation of said magnetic member;

a triggering coil wound about one leg of said magnetic core;

a charging coil wound about the other leg of said magnetic core;

a selectively operable shut-off coil wound about said other leg of said magnetic core;

an ignition transformer; and,

circuit means mounted between the legs of said magnetic core for applying a signal to the primary winding of said ignition transformer.

12. The circuit of claim I] wherein said circuit means includes an ignition capacitor and an SCR and a diode connected in series across said ignition capacitor.

l3. The circuit of claim 11 wherein said circuit means includes an SCR and voltage responsive means connected across said triggering coil to interrupt the application of a triggering potential to the gate of said SC R.

14. The circuit of claim 11 wherein said transformer and said magnetic core are potted to form a unitary structure 15. The circuit of claim 14 wherein said transformer includes a ferrite core.

16. An ignition circuit for an internal combustion engine comprising:

a magnetic core having two legs adapted to be mounted adjacent a rotating magnetic member of the engine with said legs displaced in the direction of rotation of said magnetic member;

a triggering coil wound about one leg of said magnetic core;

a charging coil wound about the other leg of said magnetic core;

an ignition transformer having a ferrite core; and

circuit means including an ignition capacitor and an SCR connected in series across said ignition capacitor, said circuit means being mounted between the legs of said magnetic core for applying a signal to the primary winding of said ignition transformer and said circuit means including voltage responsive means connected across said triggering coil to interrupt the application of a triggering potential to the gate of said SCR.

17. In an ignition system wherein a capacitor charging current is generated by the movement of magnetic means through flux cutting proximity to a charging coil in response to the forward rotation of an engine and wherein an electronic switch triggering current is thereafter generated by continued movement of the magnetic means through flux cutting proximity to a trigger coil in response to the forward rotation of the engine to thereby effect discharge of the capacitor through the electronic switch and a high voltage transformer to the ignition device. the method of ensuring engine cutoff by the generation of a second triggering current for the electronic switch in substantial synchronism with the generation of the capacitor charging current whereby a discharge path for the capacitor is provided substantially coextensive with the generation of the capacitor charging current. the second triggering current being generated by the movement of the magnetic means through flux cutting proximity to a second trigger coil in response to the forward rotation of the engine.

18. In an ignition system wherein a capacitor charging current is generated by the movement of magnetic means through flux cutting proximity to a charging coil in response to the forward rotation of an engine and wherein an SCR triggering current is thereafter gener ated by continued movement of the magnetic means through flux cutting proximity to a trigger coil in response to the forward rotation of the engine to thereby effect discharge of the capacitor through the electronic switch and a high voltage transformer to the ignition device the method ofensuring SCR cutoff by the interruption of the application of the triggering potential to the gate of the SCR responsively to the potential of the gate of the SCR.

19. A method comprising the steps of:

a. moving a first permanent magnet responsively to the forward rotation of an internal combustion engine in flux cutting proximity to a charging coil to thereby charge an ignition capacitor;

b. moving a second permanent magnet responsively to the forward rotation of an internal combustion engine in flux cutting proximity to a first trigger coil to thereby effect the discharge of the capacitor through a first ignition device;

c. moving a third permanent magnet responsively to the forward rotation of an internal combustion engine in flux cutting proximity to the charging coil to thereby charge the ignition capacitor;

d. moving a fourth permanent magnet responsively to the forward rotation of an internal combustion engine in flux cutting proximity to a second trigger coil to thereby effect the discharge of the ignition capacitor through a second ignition device;

e. moving the first and third permanent magnets responsively to the forward rotation of an internal combustion engine in flux cutting proximity to a shut-off coil coaxial with the charging coil; and,

f. selectively utilizing the output signal from the shutoff coil to prevent the charging of the ignition capacitor to ignition potential.

20. An ignition circuit for an internal combustion engine comprising:

an ignition capacitor;

an SCR;

an ignition transformer;

a magnetic core having two legs adapted to be mounted adjacent to a rotating magnetic member of an engine with said legs displaced in the direction of rotation of said magnetic member;

a triggering coil wound about one leg of said magnetic core, said triggering coil being connected to the gate of said SCR;

series with said SCR and the primary winding of said ignition transformer.

21. In an ignition system for an internal combustion engine wherein a capacitor charging current is generated by the movement of magnetic means through flux cutting proximity to a charging coil in response to the forward rotation of an engine, and wherein an elec- 12 tronic switch triggering current is generated by movement of the magnetic means through flux cutting proximity to a trigger coil in response to the forward rotation of the engine to thereby effect discharge of a capacitor through an electronic switch and a high voltage transformer to an ignition device, the improvement in decreasing the effects of conducting debris comprising the provision of a shut-off coil and mechanical switch contacts in the trigger circuit for the electronic switch in lieu of mechanical switch contacts in the charging coil circuit, said trigger coil ensuring engine cutoff by the generation of a triggering current in substantial synchronism with the generation of the capacitor charging current. 

1. An ignition circuit for an internal combustion engine comprising: a capacitor; means for periodically applying a unidirectional current to said capacitor responsively to engine rotation; a discharge circuit for said capacitor, said discharge circuit including the primary winding of an ignition transformer and an SCR connected in series; a trigger circuit means for periodically applying a triggering potential to the gate of said SCR responsively to engine rotation; and, selectively operable means for periodically applying a triggering potential to the gate of said SCR during the application of said unidirectional current to said capacitor.
 2. The circuit of claim 1 wherein said trigger circuit means includes voltage responsive means for interrupting the application of triggering potential to the gate of said SCR.
 3. The circuit of claim 1 including at least one additional discharge circuit with the primary winding of an ignition transformer and an SCR connected in series; and, a triggering circuit for each of said additional trigger circuits for periodically applying a triggering potential to the gate of the associated SCR responsively to engine rotation.
 4. An ignition circuit for an internal combustion engine comprising: a capacitor; means for periodically applying a unidirectional current to said capacitor responsively to engine rotation in the forward direction; a discharge circuit for said capacitor, said discharge circuit including the primary winding of an ignition transformer in series with electronic switch means; a trigger circuit for periodically applying a triggering potential to said switch means responsively to engine rotation in the forward direction; and, means for interrupting the application of triggering potential to said switch means responsive to said trigger circuit means.
 5. The circuit of claim 4 wherein said triggering potential interrupting means is responsive to the potential of the gate of said switch means.
 6. The circuit of claim 4 wherein said electronic switch is an SCR; and, Wherein said triggering potential interrupting means includes coil means and switching means for effectively shunting the current induced in said coil means away from the gate of said SCR.
 7. The circuit of claim 6 including selectively operable means for periodically applying a triggering potential to the gate of said SCR in substantial synchronism with the application of said unidirectional current to said capacitor.
 8. The circuit of claim 6 including impedance means connected in series with said coil means for limiting the triggering potential to a value nondestructive of said SCR at maximum engine speeds.
 9. The circuit of claim 4 including selectively operable means for periodically applying a triggering potential to said switch means in substantial synchronism with the application of said unidirectional current to said capacitor.
 10. The circuit of claim 4 including at least one additional discharge circuit for said capacitor, each of said additional discharge circuits including the primary winding of an ignition transformer in series with electronic switch means; a trigger circuit for each of said additional discharge circuits for periodically applying a triggering potential to the associated switch means responsive to engine rotation; and, means associated with each of said additional discharge circuit for interrupting the application of triggering potential to said switch means.
 11. An ignition circuit for an internal combustion engine comprising: a magnetic core having two legs adapted to be mounted adjacent to a rotating magnetic member of an engine with said legs displaced in the direction of rotation of said magnetic member; a triggering coil wound about one leg of said magnetic core; a charging coil wound about the other leg of said magnetic core; a selectively operable shut-off coil wound about said other leg of said magnetic core; an ignition transformer; and, circuit means mounted between the legs of said magnetic core for applying a signal to the primary winding of said ignition transformer.
 12. The circuit of claim 11 wherein said circuit means includes an ignition capacitor and an SCR and a diode connected in series across said ignition capacitor.
 13. The circuit of claim 11 wherein said circuit means includes an SCR and voltage responsive means connected across said triggering coil to interrupt the application of a triggering potential to the gate of said SCR.
 14. The circuit of claim 11 wherein said transformer and said magnetic core are potted to form a unitary structure.
 15. The circuit of claim 14 wherein said transformer includes a ferrite core.
 16. An ignition circuit for an internal combustion engine comprising: a magnetic core having two legs adapted to be mounted adjacent a rotating magnetic member of the engine with said legs displaced in the direction of rotation of said magnetic member; a triggering coil wound about one leg of said magnetic core; a charging coil wound about the other leg of said magnetic core; an ignition transformer having a ferrite core; and circuit means including an ignition capacitor and an SCR connected in series across said ignition capacitor, said circuit means being mounted between the legs of said magnetic core for applying a signal to the primary winding of said ignition transformer and said circuit means including voltage responsive means connected across said triggering coil to interrupt the application of a triggering potential to the gate of said SCR.
 17. In an ignition system wherein a capacitor charging current is generated by the movement of magnetic means through flux cutting proximity to a charging coil in response to the forward rotation of an engine and wherein an electronic switch triggering current is thereafter generated by continued movement of the magnetic means through flux cutting proximity to a trigger coil in response to the forward rotation of the engine to thereby effect dIscharge of the capacitor through the electronic switch and a high voltage transformer to the ignition device, the method of ensuring engine cutoff by the generation of a second triggering current for the electronic switch in substantial synchronism with the generation of the capacitor charging current whereby a discharge path for the capacitor is provided substantially coextensive with the generation of the capacitor charging current, the second triggering current being generated by the movement of the magnetic means through flux cutting proximity to a second trigger coil in response to the forward rotation of the engine.
 18. In an ignition system wherein a capacitor charging current is generated by the movement of magnetic means through flux cutting proximity to a charging coil in response to the forward rotation of an engine and wherein an SCR triggering current is thereafter generated by continued movement of the magnetic means through flux cutting proximity to a trigger coil in response to the forward rotation of the engine to thereby effect discharge of the capacitor through the electronic switch and a high voltage transformer to the ignition device, the method of ensuring SCR cutoff by the interruption of the application of the triggering potential to the gate of the SCR responsively to the potential of the gate of the SCR.
 19. A method comprising the steps of: a. moving a first permanent magnet responsively to the forward rotation of an internal combustion engine in flux cutting proximity to a charging coil to thereby charge an ignition capacitor; b. moving a second permanent magnet responsively to the forward rotation of an internal combustion engine in flux cutting proximity to a first trigger coil to thereby effect the discharge of the capacitor through a first ignition device; c. moving a third permanent magnet responsively to the forward rotation of an internal combustion engine in flux cutting proximity to the charging coil to thereby charge the ignition capacitor; d. moving a fourth permanent magnet responsively to the forward rotation of an internal combustion engine in flux cutting proximity to a second trigger coil to thereby effect the discharge of the ignition capacitor through a second ignition device; e. moving the first and third permanent magnets responsively to the forward rotation of an internal combustion engine in flux cutting proximity to a shut-off coil coaxial with the charging coil; and, f. selectively utilizing the output signal from the shut-off coil to prevent the charging of the ignition capacitor to ignition potential.
 20. An ignition circuit for an internal combustion engine comprising: an ignition capacitor; an SCR; an ignition transformer; a magnetic core having two legs adapted to be mounted adjacent to a rotating magnetic member of an engine with said legs displaced in the direction of rotation of said magnetic member; a triggering coil wound about one leg of said magnetic core, said triggering coil being connected to the gate of said SCR; a charging coil wound about the other leg of said magnetic core, said charging coil being connected to said ignition capacitor by a circuit excluding mechanical switch contacts; a shut-off coil wound about said other leg of said magnetic core, said shut-off coil being connected to the gate of said SCR through mechanical contacts; and, circuit means connecting said ignition capacitor in series with said SCR and the primary winding of said ignition transformer.
 21. In an ignition system for an internal combustion engine wherein a capacitor charging current is generated by the movement of magnetic means through flux cutting proximity to a charging coil in response to the forward rotation of an engine, and wherein an electronic switch triggering current is generated by movement of the magnetic means through flux cutting proximity to a trigger coil in response to the forward rotation of the engine to tHereby effect discharge of a capacitor through an electronic switch and a high voltage transformer to an ignition device, the improvement in decreasing the effects of conducting debris comprising the provision of a shut-off coil and mechanical switch contacts in the trigger circuit for the electronic switch in lieu of mechanical switch contacts in the charging coil circuit, said trigger coil ensuring engine cutoff by the generation of a triggering current in substantial synchronism with the generation of the capacitor charging current. 